Process and apparatus for continuous production of foam sheets

ABSTRACT

Foam sheets are continuously produced by metering foam particles, which are free of any added binder or adhesive, from a storage location onto a moving conveyor at a controlled volumetric rate so as to continuously form a layer of the particles on the conveyor, heating the layer of particles to a temperature sufficient to render the particles tacky such that the particles adhere to one another so as to form a substantially integral sheet, compressing the sheet with a compression device that applies pressure on the advancing sheet so as to compress the sheet to a smaller thickness and enhance the integrity of the sheet; and cooling the compressed sheet.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of the filing date of U.S.Provisional Patent Application Ser. No. 60/745,615 filed on Apr. 26,2006, the entire disclosure of which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

The present disclosure relates to the production of polymer foam sheets,planks, and the like. More particularly, the present disclosure relatesto a process for converting cross-linked, closed-cell polymer (e.g.,polyethylene or ethylene-vinyl acetate (EVA)) foam materials into a widerange of engineered sheet or plank products of indefinite length, and toan apparatus for carrying out such a process. The starting foammaterials may be derived from virgin or postindustrial waste sources, orfrom a combination of both. Greater cost efficiencies are achieved whena greater percentage of the starting material is obtained from wastesources.

It is known to shred, grind, or otherwise comminute cross-linkedclosed-cell foam starting materials into particulate form, and tothereafter heat fuse or flame laminate the particles together underpressure to form laminated sheet or plank products. Two basic types oftechnologies are known for producing such sheet or plank products fromcross-linked, closed-cell polyethylene or ethylene-vinyl acetate (EVA)foam starting materials. The first of these prior art technologies,commonly known as the “chimney” process, is exemplified by the processof U.S. Pat. No. 4,417,932 (Breitscheidel et al.), the disclosure ofwhich is hereby incorporated by reference. The Breitscheidel and othersimilar chimney processes introduce the comminuted foam particles bygravity into a hot air chamber or “chimney”, where the particles orgranules are exposed to temperatures in the range of between about 100°C. and about 200° C. as they fall by gravity onto a moving bottomconveyor, where they fuse with one another. This bottom conveyor carriesthe particles accumulating at the bottom of the chimney toward asecondary top conveyor that compacts the fused particles between bothconveyors into a sheet-like layer of target thickness prior to coolingby water and/or air.

The limitations of such chimney processes include the following, withoutlimitation: i) it is difficult to control dosing or the amount of foamparticles introduced into the chimney heating chamber to achieve andmaintain a uniform end product; ii) gravity feeding produces unevenexposure to heat (heavier particles fall faster, having shorter heatingor “dwell” time), thus causing inconsistent quality and strength of thefinished product; iii) light particles under the same constanttemperature spend more time in the heating chamber (longer dwell time)and are thus are over-exposed to temperature which, in turn, overheatsthe lighter particles causing blistering or complete deteriorationthereof, with the result being partial or no fusion and inconsistentquality of the end product; iv) gravity feeding into the chimney isconfined to the use of foam particles having approximately the samedensity, weight and/or dimensions to maintain uniformity of finishedproduct, which limits the use of chimney heating technology to foamshaving equal particle weight, thickness, and size; v) because chimneyheating is based on temperature and dwell time exposure, and because thedensity, specific gravity, and fusion temperature of cross-linked,closed-cell foam starting materials vary significantly from one foam toanother, it is therefore not possible to use the conventional chimneytechnology for a broad range of foam staring materials, combined orotherwise; and finally vi) the nature of the chimney technology also hasinherent difficulty in providing an even distribution of fusedparticles. Once the particles are fused at the bottom of the chimney, itis extremely difficult to produce an even thickness or density on thesheet-forming conveyor, which results in end products of inconsistentquality and limited end use applications. Thus, because chimneyheat-fusion technology is confined to specific foam starting materialshaving uniform particle size, thickness, weight and density, and becausethe finished products of this technology lack product consistency interms of dimensional tolerances and product density, it has thereforeexperienced limited market acceptance.

The second type of prior art technology known for producing laminatedsheet or plank products from cross-linked, closed-cell foam startingmaterials is known as “press batch” type technology. This technology isa batch process operation, which produces a foam sheet or plank that islimited in its dimensions to the size of the press bed, the female moldportion resting thereon, and the platen used as the (male) mold closure.More particularly, in this process, the comminuted cross-linked foamparticles are dispensed manually into a cavity of the female moldportion. The press platen is then lowered to close the mold cavity(pressure being optional, subject to the desired finished product), andthe necessary heat is transferred by conduction from the heated platenand/or from the female mold into the foam workpiece to form the endproduct.

Shortcomings of the press batch type of technology include thefollowing, without limitation: i) the process is limited to producingfoam sheets or planks one at a time (i.e., it is not a continuousprocess; ii) the product is limited to the dimensions of the femalemould cavity and the cooperating press platen; iii) the foam startingmaterial used must be shredded or otherwise comminuted to a size rangingfrom about 1″ (25 mm) to about 2″ (50 mm), with a thickness greater thanabout ¼″ (6 mm), in order to promote adequate bonding between theparticles of the resulting sheet or plank; and iv) the thickness of thesheets or planks produced is limited, because there is a limit to howmuch sheet thickness can be heated by convective heating into theinterior of the sheet. The outer surfaces of the sheet tend to be heatedto a higher temperature than the interior of the sheet, therebyresulting in non-uniform bonding between the foam particles through thesheet thickness. Thus, the press batch technology is limited to arelatively narrow range of foam starting materials and a relatively thinend product, and is relatively expensive because of its time-consumingbatch nature and the use of relatively expensive, close-tolerance molds.Accordingly, press batch type technology is of limited application, andis not cost-effective in the marketplace, particularly wherehigh-volume, large-sized end products are required.

BRIEF SUMMARY OF THE DISCLOSURE

The present disclosure relates to an improved, cost-effective processand apparatus for continuous production of foam sheets or planks ofindefinite length from cross-linked, closed-cell polyethylene orethylene-vinyl acetate (EVA) foam materials derived from virgin and/orpostindustrial foam waste starting materials. The sheets or planks canbe, but are not limited to being, from about 2 lb/ft³ (32 kg/m³) toabout 12 lb/ft³ (190 kg/m³) in density, from about ¼ inch (6 mm) toabout 2.5 inches (64 mm) in thickness, from about 4 ft (1.2 m) to about8 ft (3.6 m) in width, at a production rate of about 5 ft/min (1.5m/min) to about 20 ft/min (6 m/min).

The finished product made by the presently disclosed process andapparatus is consistent in quality, and maintains dimensional andperformance specifications for a wide range of applications, including,by way of example and without limitation, floating lagoon covers,underlay drainage and impact layers for sports fields having anartificial turf overlay, playground safety surfaces, and buildingproducts such as insulated wall and floor panels. Either or both of thetop and/or bottom surface(s) of the foam planks or sheets so producedmay be substantially smooth, grooved, embossed, cross-hatched, orotherwise patterned by effecting relatively minor variations tocomponents of the compression and cooling device of the apparatus,thereby lending further flexibility to the process and apparatus and therange of products capable of production therefrom. A textile layer mayoptionally be adhered to one and/or both of the top and bottomsurface(s) of the foam planks or sheets during production to stillfurther extend the variety and utility of the products.

While the method and apparatus disclosed are advantageous for producingfoam products having a wide range of finished thicknesses, they areespecially valuable for producing foam sheet or plank products havinggreater thicknesses (e.g., greater than about 50 mm or 2 inches) andgreater product consistency than heretofore readily available in theprior art. Such foam-based products lend themselves to use in a widespectrum of applications not previously available for this class ofproduct.

In accordance with one embodiment, the process comprises the steps of:

-   -   (a) metering the particles, which are free of any added binder        or adhesive, from a storage location onto a moving conveyor at a        controlled volumetric rate so as to continuously form a layer of        the particles on the conveyor;    -   (b) heating the layer of particles to a temperature sufficient        to render the particles tacky such that the particles adhere to        one another so as to form a substantially integral sheet;    -   (c) compressing the sheet with a compression device that applies        pressure on the advancing sheet so as to compress the sheet to a        smaller thickness and enhance the integrity of the sheet; and    -   (d) cooling the compressed sheet.

More particularly, the metering step comprises using a variabledispensing device to dispense the particles onto the conveyor, thevariable dispensing device being variable in geometry for adjusting asize of an opening through which the particles are dispensed so as toregulate the volumetric rate at which the particles are dispensed.

The present disclosure also relates to an apparatus for continuouslyproducing polymer foam sheets or planks from starting polymer foammaterial comprising virgin and/or postindustrial polymer foam materialsthat have been comminuted into particles. In one embodiment, theapparatus comprises (a) a metering device including a moving conveyorand being structured and arranged to meter the particles, which are freeof any added binder or adhesive, from a storage location onto the movingconveyor at a controlled volumetric rate so as to continuously form alayer of the particles on the conveyor; (b) a heating device structuredand arranged to heat the layer of particles to a temperature sufficientto render the particles tacky such that the particles adhere to oneanother so as to form a substantially integral sheet; (c) a compressiondevice structured and arranged to apply pressure on the advancing sheetso as to compress the sheet to a smaller thickness and enhance theintegrity of the sheet; and (d) a cooling device for cooling thecompressed sheet.

In one embodiment, the metering device includes a variable dispensingdevice to dispense the particles onto the conveyor, the variabledispensing device being variable in geometry for adjusting a size of anopening through which the particles are dispensed so as to regulate thevolumetric rate at which the particles are dispensed.

The storage location for the particles can comprise a hopper having abottom wall sloping downward toward a front wall of the hopper. In thiscase, the variable dispensing device comprises a metering gate adjacentan opening in the front wall of the hopper, a metering aperture beingdefined between the metering gate and the bottom wall through which theparticles flow aided by the influence of gravity, the metering gatebeing adjustable in position for regulating the metering aperture.

In one embodiment, the process comprises the step of contacting thelayer of particles on the moving conveyor so as to regulate thethickness of the layer before the layer is advanced to the heating step.Optionally, the contacting step can also regulate the width of the layeron the moving conveyor.

In an exemplary embodiment, the contacting step comprises contacting thelayer of particles with at least one rotating device havingcircumferentially spaced members for contacting the particles, the atleast one rotating device being rotatably driven such that said membersmove in a direction opposite to a direction of travel of the conveyor assaid members contact the particles.

In one embodiment, the at least one rotating device comprises first andsecond rotating devices spaced apart along the direction of travel ofthe conveyor and each having said members moving in the directionopposite to the direction of travel of the conveyor. The second rotatingdevice is downstream of the first rotating device along the direction oftravel of the conveyor, and the vertical spacing between said members ofthe second rotating device and the conveyor is smaller than the verticalspacing between said members of the first rotating device and theconveyor.

To regulate the thickness of the layer on the conveyor, the process caninclude the step of adjusting a vertical spacing between said members ofthe or each rotating device and the conveyor.

In one embodiment, the step of heating the layer comprises advancing thelayer through a heating device comprising a housing that defines asubstantially enclosed interior, and circulating heated air through theinterior of the housing. The interior of the housing is divided intosubstantially separate first and second chambers, the second chamberbeing downstream of the first chamber in the direction of travel of thelayer through the housing. The step of circulating heated air comprisescirculating a first portion of the heated air through the first chamberin a first direction and circulating a second portion of the heated airthrough the second chamber in a second direction different from thefirst direction.

As one example, one of the first and second directions can be generallyvertically downward and the other of the first and second directions canbe generally vertically upward.

The process can further comprise the step of adjusting the speed oftravel of the layer through the heating device so as to adjust a dwelltime of the layer in the heating device.

In some embodiments, an upper surface of the layer is not contacted byany belt or any part of the heating device as the layer travels throughthe heating device.

Advantageously, the cooling step takes place concurrently with thecompressing step. As an example, the cooling step can comprisecontacting the sheet with chilled water.

The compressing step can comprise advancing the sheet on a conveyorthrough a nip defined between the conveyor and a compression member. Thecompression member can comprise a compression belt, or one or morecompression rollers. In some embodiments, the compression member isoperable to emboss the sheet with a predetermined embossing pattern.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Having thus described the invention in general terms, reference will nowbe made to the accompanying drawings, which are not necessarily drawn toscale, and wherein:

FIG. 1 is a perspective view of an apparatus for continuously producingpolymer foam sheets or planks in accordance with one embodiment of theinvention;

FIG. 2 is a perspective view of a metering device in accordance with oneembodiment of the invention;

FIG. 3 is a side view, partly in section, of the metering device of FIG.2;

FIG. 4 is a side view, partly in section, of a heating device inaccordance with one embodiment of the invention;

FIG. 5 is a side view, partly in section, of a cooling device andcompression device in accordance with one embodiment;

FIG. 6 is a side view, partly in section, of a cooling device andcompression device in accordance with another embodiment of theinvention;

FIG. 6A is a view along line 6A-6A in FIG. 6;

FIG. 6B is a cross-sectional view through the sheet formed by thecooling device and compression device of FIG. 6;

FIG. 6C is a perspective view of a portion of the device of FIG. 6;

FIG. 7 is a side view, partly in section, of a compression device andcooling device in accordance with a further embodiment of the invention;

FIG. 7A shows a portion of the device of FIG. 7, as viewed along thedirection of travel of the sheet through the device;

FIG. 7B shows a compression roller of the device of FIG. 7; and

FIG. 7C is a perspective view of a portion of the device of FIG. 7.

DETAILED DESCRIPTION OF THE DRAWINGS

The present invention now will be described more fully hereinafter withreference to the accompanying drawings in which some but not allembodiments of the inventions are shown. Indeed, these inventions may beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will satisfy applicable legalrequirements. Like numbers refer to like elements throughout.

Referring now to FIG. 1, there is illustrated by way of non-limitingexample an apparatus 20 according to one embodiment of the presentinvention for the production of engineered sheet or plank products ofindefinite length from comminuted, cross-linked, closed-cell polymer(e.g., polyethylene or ethylene-vinyl acetate (EVA)) foam particles,which products may be subsequently cut to desired variable lengths. Theapparatus 20 comprises a continuous processing line for the productionof such sheet or plank products. The apparatus includes a meteringsection 22, illustrated on a larger scale in FIGS. 2 and 3, wherein thecomminuted foam particles 24 are fed from a hopper 26 at a controlledrate onto a first conveyor 28 for further metering into a pro-formaparticulate layer 27 by one or more adjustable paddlewheel devices 29mounted within the metering section 22.

The apparatus 20 further comprises a heating device 30, illustrated on alarger scale in FIG. 4, wherein the comminuted foam particles 24 passfrom the metering section 22 onto a second conveyor 32 for transportthrough a two stage heating/fusion oven 34, wherein the pro-form aparticulate layer 27 of comminuted foam particles 24 is evenly heatedthroughout under closely controlled conditions to cause fusing togetherof the particles making up such layer 27 to form a continuous fusedpre-sheet 36 of laminated foam particles. The pre-sheet 36 is ofintermediate thickness to the pro-forma particulate layer 27 and thefinished sheet S produced by the apparatus 20.

The apparatus 20 also includes a compression and cooling device 40, oneembodiment of which is illustrated on a larger scale in FIG. 5. Thecompression and cooling device 40 is designed to compress and cool thefused pre-sheet 36 moving therethrough on the second conveyor 32 tothereby produce a finished sheet S having smooth upper and lowersurfaces.

Two alternative embodiments of the compression and cooling device areillustrated in detail in FIGS. 5, 6A, 6B, and 6C (wherein the firstalternative compression and cooling device is designated by thereference numeral 40 a) and in FIGS. 7, 7A, 7B, and 7C, (wherein thesecond alternative embodiment is designated by the reference numeral 40b), wherein changes to the various rollers and belts used therein arerespectively illustrated, the effect of such first and secondalternatives being to produce finished sheets S having embossed uppersurfaces of differing patterns.

All of the above-described components of the apparatus 20 are describedin further detail below.

Starting Materials

The raw starting materials used in the process and by the apparatus ofthe present invention preferably comprise postindustrial closed-cellpolyethylene, cross-linked polyethylene, and EVA foam waste of variousdensities, shapes, and colors, generated by polyethylene foammanufacturers, converters, and fabricators. One large source of suchsuitable waste is the automotive industry, which generates huge volumesof this material from automotive interior and under-hood sound deadeningand heat insulating applications. In the absence of a cost-effectiveprocess for reusing or recycling of such foam waste, as represented bythe present invention, extremely large volumes of this type of foamwaste currently end up in landfill sites. Typically this foam waste isshipped for recycling in bails, buns on skids, or in large plastic bags.While some of this incoming waste may be sorted and stored according tothe density and quality of foam therein, a significant majority thereofhas a mixed density and quality content, which has been a severe limitto its further usage in the prior art. A significant advantage of thepresent invention is that waste of such mixed density and quality canstill be utilized to produce usable end product sheets by the processand apparatus of the present invention.

Preparing the Foam Waste for Subsequent Processing

Waste foam is selected for initial shredding according to density,melting point, coefficient of expansion, and fusing qualities. Bails,bags or loose foam waste are placed onto a conveyor (not shown) feedinga shredder or shredders (also not shown). The function of theshredder(s) is to comminute the multitude of various waste foam startingshapes to irregular, granular shaped comminuted foam particles 24 havingfrom about ½″ diameter to about 2″ diameter, depending upon the desiredend-use application. The hourly capacity of the shredder or shreddersshould be matched to the hourly consumption of the foam processingapparatus 20.

The granular particles are then transported from the shredder(s) by airor auger transport means (not shown) to a holding bin (also not shown)where dust and surplus air are removed. The function of the holding binis to hold a sufficient amount of comminuted foam particles 24 as areserve in the event the upstream shredder capacity cannot keep up withthe processing consumption of the apparatus 20, or in the event of amalfunction of the shredder(s). The holding bin (not shown) can be ofalmost any shape and/or holding capacity, preferably providing a minimumholding capacity of 4 to 6 hours of the process requirements of theapparatus 20.

From the holding bin (not shown) the comminuted foam particles 24 aretransported by air or auger transport means through a supply tube T tothe hopper 26 (FIG. 2). The function of the hopper 26 is to deliver theappropriate volumetric flow rate of foam particles 24 to the firstconveyor 28 on an operatively continuous basis as determined by theparameters (most notably, thickness, density and porosity) desired forthe finished sheets S. The belt of the first conveyor 28 is preferablyconstructed from stainless steel mesh or the like, and may or may not beTEFLON® (PTFE) coated to resist sticking of the foam particles. The sizeof the hopper 26 is subject to the processing volume requirements of theapparatus 20, and should typically hold, for example, from about 50 toabout 100 cubic feet of foam particles having from about ½″ to about 2″diameters.

With reference to FIGS. 2 and 3, the hopper preferably includes avibrating mechanism 52 driven by an electric motor 54 and connected toan inclined floor 56 of the hopper 26 in such a manner that the foamparticles 24 within the hopper 26 are continually being agitated toprevent their bridging or compacting within the hopper, which bridgingor compacting would hinder the free flow of the particles from thehopper. The hopper is further equipped with an adjustable dispensinggate 58 that controls the flow of foam particles through an opening inthe front wall 26 a of the hopper to a rate predetermined according tothe required thickness and width of the finished sheet product. Thewidth dispensing range is preferably from about 24″ to about 72″ wide,with a thickness range preferably from about 1″ to about 16″ thick. Thedispensing gate 58 is pivotally mounted on the front wall 26 a such thatthe gate pivots about its upper edge, and is adjustable by a pair ofbiasing devices 60, 60 located adjacent opposite lateral edges of thedispensing gate 58 and interconnected between the front wall 26 a andthe dispensing gate 58. Each of the biasing devices 60 may be a coilspring as shown, or, for example, a gas load strut (not shown).Adjustment of the strength of the biasing devices 60 varies the degreeof opening of the dispensing gate 58, and hence the rate of flow of thefoam particles through the opening in the front wall of the hopper.Thus, interchanging one pair of biasing devices 60, 60 for another pairof biasing devices of different strength is one way of variablycontrolling the flow of the foam particles from the hopper;alternatively, variable strength biasing devices 60, for example,adjustable gas load struts, (not shown) may be employed to effect suchrate control. Of course, it is also possible to use controllableactuators (e.g., electric motor-powered mechanisms, hydraulicactuator-powered mechanisms, or the like) for regulating the position ofthe gate 58, if desired.

The foam particles 24 are in this manner dispensed at a predeterminedrequired volumetric rate from the hopper 26 down the angled floor 56 ina predetermined width (determined by the width of the floor 56 and ofthe first conveyor 28) and in a controlled thickness (determined by thedegree of opening of the dispensing gate 58) onto the first conveyor 28positioned thereunder. A pair of optional edge skirts 28 a, 28 b (FIG.2) can be mounted on opposite sides of the first conveyor 28 to preventspillage of the foam particles from the first conveyor. A textile sheet(not shown) optionally can be placed over both the first conveyor 28 andsecond conveyor 32 to feed continuously therealong with the pro-formaparticulate layer 27, thereby forming a base substrate that will bebecome adhered to the lower surface of the fused pre-sheet 36 as itpasses through the heating/fusion oven 34. This textile sheet ispreferably a polyester textile sheet, and not only assists in preventingthe foam particles from adhering to the first and second conveyors ofthe apparatus 20, but also provides further structural integrity to thefinished planks or sheets S, and adapts them for a variety of additionalend uses.

Once the measured layer of foam particles 24 is dispensed onto the firstconveyor 28 or onto the textile-covered first conveyor 28 as the casemay be, the layer passes under one or more height-adjustable paddlewheeldevices 29 mounted within the metering section 22 of the apparatus 20.Two such paddlewheel devices 29 are shown in the drawings, one mounteddownstream (i.e., in the direction of travel of the foam particle layer)of the other. The paddlewheel devices 29 are each rotatably mountedabove the first conveyor 28 on a respective paddlewheel frame 31, eachof which frames is independently adjustable in both vertically upwardand vertically downward directions, as indicated by double-headed arrowsB of FIG. 3. The paddlewheel devices 29 each has a plurality of primaryarms 29 a extending radially outwardly from the central axis of thepaddlewheel device 29, with each primary arm 29 a having a secondary arm29 b pivotally mounted adjacent its outer edge to freely hang in gravitydependent relation therefrom for contacting the foam particles as theyare carried therebeneath by the first conveyor 28. Each of thepaddlewheel devices 29 is rotatably driven in the clockwise direction(indicated by arrows D, D of FIG. 3), such that the secondary arms 29 bhave a significant component of horizontal motion in the oppositedirection of movement of the foam particle layer carried by the firstconveyor 28 as the secondary arms contact the foam particles. Verticaladjustment of the paddlewheel frame 60 allows the gap defined betweenthe free end of each secondary arm 29 b and the top surface of the firstconveyor 28 (or the top surface of the optional textile sheet lying atopthe first conveyor 28) to be adjusted. This, in turn, permits variationof the thickness of the layer of foam particles passing thereunder toform the pro-forma particulate layer 27. Thus, one or more paddlewheeldevices 29 constructed, arranged, and operating in the general mannerdescribed above assure that the required height and width of foamparticles which make up the pro-forma particulate layer is maintainedand evenly distributed. Such even distribution is critical to theproduction of an end sheet or plank product S having uniform physicalcharacteristics. It will be understood, however, that the presentinvention can be practiced with paddlewheel devices, or more generallyother types of rotary devices, of configurations different from theparticular paddlewheel devices 29 as illustrated and described herein.

The paddlewheel devices 29 should, but need not be, constructed andotherwise adapted to be adjustable from about 24″ to about 72″ in width,and the gap described above should be, but need not be, adjustable fromabout 1″ to about 16″ in height, depending upon the requirements of thefinished sheet or plank product. It will also be appreciated that othertypes of devices for contacting the layer of particles on the movingfirst conveyor can be employed, if desired.

Following the progression depicted in FIG. 3, the first conveyor 28hands off the pro-form a particulate layer 27 to the second conveyor 32just before the layer enters the heating/fusion oven 34. The belt of thesecond conveyor 32 is preferably constructed from stainless steel meshor the like, and may or may not be TEFLON® (PTFE) coated to resiststicking of the foam particles 24 thereto. The aforesaid transfer of thepro-forma particulate layer to the second conveyor 32 is furtherfacilitated where the aforementioned optional textile layer (not shown)is used. In this latter case, the textile layer also passes from the topsurface of the first conveyor 28 onto the top surface of the secondconveyor 32 as it carries the pro-forma particulate layer. In eithercase, the second conveyor 32 transports the pro-forma particulate layer27 of relatively uniform thickness through an upstream end of theheating/fusion oven 34 into its interior. It is also possible to arrangethe first conveyor 28 to extend through the oven 34, such that no secondconveyor is required. In any event, during passage through the interiorof the oven 34, the pro-forma particulate layer 27 can be reduced inthickness by as much as 50% to 75%, depending upon the type, density,and melting point of a given foam waste starting material. The averagethickness reduction is in the range of about 60%.

The function of the heating/fusion oven 34, which is desirably but notnecessarily powered by natural gas, fuel oil, or electricity, is to fuseor weld the foam particles together to achieve a homogeneous foam sheetor plank S. This is accomplished by heating the particles 24sufficiently such that at least the surfaces of the particles 24 melt orpartially melt so as to be rendered soft and tacky, the tacky particlesthen fusing together. It is advantageous in this regard that the heat ofthe oven be evenly distributed and within +/−2 degrees Celsius of thetarget design temperature, which for the foam materials mentioned hereinis typically in the range of from about 115 degrees Celsius (239 degreesFahrenheit) to about 180 degrees Celsius (356 degrees Fahrenheit),subject to specific foam particle makeup. Average operating temperaturesfor the oven 34 for these types of foam materials are typically in therange of about 138 degrees Celsius (280 degrees Fahrenheit) to about 160degrees Celsius (320 degrees Fahrenheit), subject again to specific foamparticle makeup.

In order to achieve such even heating within the heating/fusion oven 34and within the fused pre-sheet 36, it is advantageous that theheating/fusion oven 34 be divided into two or more internal heatingchambers having alternating cross-flow heating air currents, asillustrated in FIG. 4. Thus, it will be seen that the heating/fusionoven 34 is transversely bisected by a vertical interior dividing wall70, having an opening for passage of the fused pre-sheet 36therethrough, so as to form two substantially separate internal heatingchambers of generally equal volume. The first of the internal heatingchambers is the upstream chamber labeled “Chamber #1” in FIG. 4. Thesecond of the internal heating chambers is the adjacent downstreamchamber labeled “Chamber #2”. Both Chamber #1 and Chamber #2 are heatedby hot air convection currents that flow through each of the heatingchambers in opposite directions. That is, in Chamber #1, the hot airconvection currents 72 enter the chamber through downwardly directedsupply nozzles 74 arranged along the top of Chamber #1 and exit Chamber#1 through a return duct 76 arranged along the bottom of Chamber #1adjacent to the dividing wall 70. This cross-chamber air flow in Chamber#1 is represented in FIG. 4 by small arrows F. In contrast, in Chamber#2, the hot air convection currents 78 enter the chamber throughupwardly directed supply nozzles 80 arranged along the bottom of Chamber#2, and exit Chamber #2 through return vents 82 arranged along the topof Chamber #2. This cross-chamber air flow in Chamber #2 is representedin FIG. 4 by small arrows G. Having the cross-flow direction of Chamber#1 reversed from that of Chamber #2 ensures more complete and evenheating of the fused pre-sheet 36 as it moves through the heating/fusionoven 34, which even heating is essential to quality control of the endproduct foam sheet or plank, particularly where such foam sheet or plankhas a thickness greater than about 50 cm (about 2 inches). Of course, itis possible for the convection currents in Chamber #1 to flow upwardlywhile the convection currents in Chamber #2 flow downwardly. Other airflow directions can also be employed if desired.

The temperature of the hot air being introduced into Chamber #1 andChamber #2 should be in the range of about 60 degrees Celsius (about 140degrees Fahrenheit) to about 193 degrees Celsius (about 380 degreesFahrenheit), and more preferably in the range of about 82 degreesCelsius (about 180 degrees Fahrenheit) to about 204 degrees Celsius(about 400 degrees Fahrenheit), but the temperature is not limitedthereto. These temperatures work well with the foam starting materialsdiscussed above, where the second conveyor 32 is moving the fusedpre-sheet 27 through the heating/fusing oven 34 at speeds from about 1ft/min (0.3 m/min) to about 30 ft/min (9 m/min), but the process andapparatus of the invention are not limited to these values. With theserates of conveyor movement, it is possible to obtain even heatdistribution in the fused pre-sheet 27 (with resultant thorough fusionbetween the foam particles 24 thereof), while achieving oven dwell timesof about 1 minute to about 30 minutes. A more preferred dwell time inthe heating/fusion oven 34 is about 1.5 to about 6 minutes, at aconveyor speed from about 20 ft/min to about 2 ft/min, with thetemperature of the oven being about 115 degrees Celsius to about 180degrees Celsius.

The average dwell time in the heating/fusion oven 34 is about 3 minutesat a conveyor speed of 10 ft/min and a temperature of 140 degreesCelsius, subject to foam particle 24 makeup.

The fused foam particle sheet exits the oven in the form of the fusedpre-sheet 36, having a temperature in the range from about 115 degreesCelsius to about 180 degrees Celsius, with an average temperature ofabout 140 degrees Celsius.

The second conveyor 32 thereafter delivers the hot and fused foam fusedpre-sheet 36 to the compression and cooling device 40 of the apparatus20 for subsequent processing. The purpose of the compression and coolingdevice 40 is to compress the fused pre-sheet 36 to the desired thicknessand density and to cool this layer, thus producing a final sheet Shaving the desired dimensions and properties.

The compression and cooling device comprises a compression assembly 90and a cooling assembly 100. The compression assembly 90 in theembodiment of FIG. 5 comprises a pair of spaced side frames 92 (only oneof which is visible in FIG. 5), each of which has three downwardlyprojecting transversely extending leg portions 92 a, 92 b, and 92 c(i.e., six leg portions in total). Each corresponding pair of legportions has mounted for rotation therebetween, adjacent their lowerends, a respective transversely extending compression roller 93 a, 93 b,and 93 c. A compression belt 94, constructed from a water-permeablestainless steel mesh or the like (which mesh may be TEFLON® (PTFE)coated), surrounds the three compression rollers 93 a, 93 b, and 93 c toform an endless loop, and the entire compression assembly 90 isadjustable in position both vertically upward and vertically downward asindicated by double-headed arrow H. An electrical drive motor (notshown) drives at least one of the compression rollers 93 a, 93 b, and/or93 c in a counter-clockwise direction as seen in FIG. 5, which, in turn,causes the compression belt 94 to rotate in the same general direction,as indicated by the arrows I of FIG. 5. Vertical adjustment of theposition of the compression assembly 90 allows the nip formed betweenthe compression belt 94 and the top surface of the second conveyor 32 tobe adjustable in height so as to accommodate the formation of finishedsheets or planks of variable thickness. Moreover, downward pressureexerted by the compression assembly 90 (through the agency of therollers 93 a, 93 b, and 93 c acting on the compression belt 94) on thefused pre-sheet 36 entering the nip can also be readily varied byvertical adjustment of the compression assembly 90 to thereby adjust thedensity of the finished sheets or planks. In this latter regard, thecompression assembly 90 should desirably have a capacity of developingpressure from about 20 psi to about 500 psi on the fused pre-sheet 36passing through the nip, the variance being determined by the densityrequirement of the finished sheets or planks, which sheets or plankshave substantially smooth upper and lower surfaces in the embodiment ofFIG. 5. The average compression pressure used is typically in the rangeof about 50 psi to about 500 psi.

As previously noted, the pro-forma particulate layer 27 entering theheating/fusion oven 34 typically may decrease in thickness by about 60%or more by the time the layer exits the heating/fusion oven 34 as thefused pre-sheet 36. Moreover, a further thickness decrease of about 50%may typically be encountered as between the fused pre-sheet 36 enteringthe nip of the compression assembly 90 and the sheet or plank S exitingfrom the compression assembly 90.

Once the desired thickness and densities are achieved in the regionbetween the front two compression rollers 93 a and 93 b, the compressedfoam sheet or plank is rapidly cooled by the cooling assembly 100, whilestill in the desired compression mode, with chilled water emitted fromspray nozzles 97 formed on the underside of a water supply header 96,which supply header 96 is preferably positioned between the secondcompression roller 93 b and third 93 c compression roller. The sprayedcooling water is collected below the second conveyor 32 by a catchmentbasin 98, and is continuously recirculated therefrom through aconventional chiller system (not shown) that maintains the cooling waterat a temperature range of about 15 degrees Celsius to about 45 degreesCelsius. A vacuum assist (not shown) may be applied in the region of thecatchment basin 98 to speed removal of cooling water from the sheet orplank S.

The average temperature of the cooling water is preferably about 18degrees Celsius to about 20 degrees Celsius, and the cooling water is incontact with the sheet for about 30 seconds to one minute. The coolingassembly 100 can thus be seen to essentially comprise the water supplyheader 96, the spray nozzles 97, and the catchment basin 98.

Once the foam sheet or plank S is cooled to a range of about 26 degreesCelsius to about 45 degrees Celsius, the foam sheet or plank sets to itspredetermined target dimensions. The average setting temperature for thecooled sheet or plank is in the 30 degree Celsius range, subject to linespeed and product thickness.

The compression assembly 90 can also be configured as an embossingsystem as seen in the first and second alternate embodiments depicted ineach of FIGS. 6, 6A, 6B, and 6C, and FIGS. 7, 7A, 7B, and 7C,respectively. In the drawings depicting these two alternate embodiments,similar reference figures and numerals as have been used in FIGS. 1through 5 have been retained in respect of analogous structures.

In the first alternative embodiment illustrated in FIGS. 6, 6A, 6B, and6C, the substantially smooth compression belt 94 shown in FIGS. 1through 5 is replaced by a modified compression belt 94′ havingremovable endless male embossing belts 95 attached in regular spacedrelation around the underlying compression belt 94′ so as to define aseries of valleys 97 between the embossing belts 95. Thus, as will beappreciated from FIGS. 6A and 6B, use of this modified compression andcooling device 40 a in the same general manner described above inrelation to the process and apparatus of FIGS. 1 through 5 will producea final sheet or plank S having a series of longitudinally extendinggrooves 99 (corresponding to the profile of the embossing belts 95) eachpositioned between two longitudinally extending raised lands 101 definedby the profile of the valleys 97. The longitudinal grooves 99 mayadvantageously have a depth of about ¼″ to about 1¾″ positioned on about1″ to about 12″ centers, with a typical average depth being about ½″ to¾″ on about 2″ to 2.5″ average centers.

In the second alternative embodiment illustrated in FIGS. 7, 7A, 7B, and7C, a modified compression and cooling device 40 b having no compressionbelt is depicted. Additionally, the three downwardly depending legs 92a, 92 b and 93 c of the earlier embodiments are replaced by front 92 aand rear 92 c downwardly depending legs of substantially equal length,which are joined to one another by a lower horizontal cross bar 92 d.Modified compression rollers 93 a′, 93 b′, and 93 c′ replace thecorresponding smooth compression rollers 93 a, 93 b and 93 c shownpreviously. The compression rollers 93 b′ and 93 c′ are each modified inthe same general manner to have a series of male embossing ribs 104disposed in regular spaced relation around their outer circumference. Inthis manner, they each define a series of valleys 103 between theembossing ribs 104.

The lead compression roller 93 a′ is also modified in the secondalternative embodiment to be of larger diameter than the leadcompression roller 93 a of the earlier described embodiments, and tohave a series of raised ribs 105 parallel to its rotational axis spacedaround its outside circumference. The raised ribs 105 define betweenthemselves a corresponding series of valleys 106, also aligned with therotational axis of the compression roller 93 a′. Thus, it will beappreciated from FIGS. 7, 7A, 7B, and 7C that the use of this modifiedcompression and cooling device 40 b in the same general manner describedabove will produce a final sheet or plank S having a cross-hatched uppersurface.

Trim saws (not shown) running parallel to the direction of travel of thesheet S may be advantageously used to trim or cut to a desired width,trimming on both sides, one side only, or not at all, subject to enduser requirements. Trimming width range is typically from about 36″ toabout 60″, with an average trimming width being about 48″.

From the trim saw station (not shown) the fused plank or sheet Sadvantageously enters a cut-off station (not shown) where a flying sawmoving transverse to the direction of sheet travel cuts the foam plankor sheet S to a desired length. The flying saw can automatically cut thefinished foam sheet or plank into predetermined lengths from about 36″up to about 96″, depending on customer specifications. Average cutlength is 48″ to 60″. Finished foam sheets or planks can be stacked andpalletized at the end of production line apparatus 20. Where continuousroll stock foam product is desired, the sheets can be cut from about 50feet to about 250 feet in length. Average roll-stock length is about 100feet. Finished roll-stock foam end product of any desired length can berolled up at the end of the production line apparatus 20 by means of aspecially designed winder.

Many modifications and other embodiments of the inventions set forthherein will come to mind to one skilled in the art to which theseinventions pertain having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. Therefore, it is tobe understood that the inventions are not to be limited to the specificembodiments disclosed and that modifications and other embodiments areintended to be included within the scope of the appended claims.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

1. A process for continuously producing polymer foam sheets or planksfrom starting polymer foam material comprising virgin and/orpostindustrial polymer foam materials that have been comminuted intoparticles, the process comprising the steps of: metering the particles,which are free of any added binder or adhesive, from a storage locationonto a moving conveyor at a controlled volumetric rate so as tocontinuously form a layer of the particles on the conveyor; heating thelayer of particles to a temperature sufficient to render the particlestacky such that the particles adhere to one another so as to form asubstantially integral sheet; compressing the sheet with a compressiondevice that applies pressure on the advancing sheet so as to compressthe sheet to a smaller thickness and enhance the integrity of the sheet;and cooling the compressed sheet.
 2. The process of claim 1, wherein themetering step comprises using a variable dispensing device to dispensethe particles onto the conveyor, the variable dispensing device beingvariable in geometry for adjusting a size of an opening through whichthe particles are dispensed so as to regulate the volumetric rate atwhich the particles are dispensed.
 3. The process of claim 2, furthercomprising the step of contacting the layer of particles on the movingconveyor so as to regulate the thickness of the layer before the layeris advanced to the heating step.
 4. The process of claim 3, wherein thecontacting step further regulates the width of the layer on the movingconveyor.
 5. The process of claim 3, wherein the contacting stepcomprises contacting the layer of particles with at least one rotatingdevice having circumferentially spaced members for contacting theparticles, the at least one rotating device being rotatably driven suchthat said members move in a direction opposite to a direction of travelof the conveyor as said members contact the particles.
 6. The process ofclaim 5, further comprising adjusting a vertical spacing between saidmembers of the at least one rotating device and the conveyor so as toregulate the thickness of the layer on the conveyor.
 7. The process ofclaim 5, wherein the at least one rotating device comprises first andsecond rotating devices spaced apart along the direction of travel ofthe conveyor and each having said members moving in the directionopposite to the direction of travel of the conveyor.
 8. The process ofclaim 7, further comprising adjusting a vertical spacing between saidmembers of each rotating device and the conveyor so as to regulate thethickness of the layer on the conveyor.
 9. The process of claim 8,wherein the second rotating device is downstream of the first rotatingdevice along the direction of travel of the conveyor, and the verticalspacing between said members of the second rotating device and theconveyor is smaller than the vertical spacing between said members ofthe first rotating device and the conveyor.
 10. The process of claim 1,wherein the step of heating the layer comprises advancing the layerthrough a heating device comprising a housing that defines asubstantially enclosed interior, and circulating heated air through theinterior of the housing.
 11. The process of claim 10, wherein theinterior of the housing is divided into substantially separate first andsecond chambers, the second chamber being downstream of the firstchamber in the direction of travel of the layer through the housing, andwherein the step of circulating heated air comprises circulating a firstportion of the heated air through the first chamber in a first directionand circulating a second portion of the heated air through the secondchamber in a second direction different from the first direction. 12.The process of claim 11, wherein one of the first and second directionsis generally vertically downward and the other of the first and seconddirections is generally vertically upward.
 13. The process of claim 10,further comprising adjusting the speed of travel of the layer throughthe heating device so as to adjust a dwell time of the layer in theheating device.
 14. The process of claim 10, wherein an upper surface ofthe layer is not contacted by any belt or any part of the heating deviceas the layer travels through the heating device.
 15. The process ofclaim 1, wherein the cooling step takes place concurrently with thecompressing step.
 16. The process of claim 15, wherein the cooling stepcomprises contacting the sheet with chilled water.
 17. The process ofclaim 1, wherein the compressing step comprises advancing the sheet on aconveyor through a nip defined between the conveyor and a compressionmember.
 18. The process of claim 17, wherein the compression member isoperable to emboss the sheet with a predetermined embossing pattern.